Carbon ion self–sputtering attained by sublimation of hot graphite target and controlled by pulse injection of a neon–helium gas mixture

Abstract

The operation of graphite targets with an increased temperature (HT – hot target) is studied for the case of gas injection magnetron sputtering (GIMS) of: 1) diamond–like carbon (DLC), and 2) carbon–silicon carbide (C–SiC) films. A purposely–thinned graphite target with a reduced thermal conductivity is applied for DLC deposition, extending its high temperature sputtering range up to 1636 °C. For the purpose of C–SiC synthesis four sockets with a silicon carbide powder are designed within graphite target. In this approach, the C–SiC target surface can be heated up to 1443 °C due to a greater energy input from impulse plasma, in the range 322–932 J. The HT sputtering is energy–controlled by a pulsed injection of a neon–helium gas mixture. High–energy Ne+ and He+ ions extend the length of pulsed GIMS discharge due to the self–sputtering effect observed during the deposition of DLC and C–SiC films. These conditions result in an almost 5–fold increase in the film growth rate (up to 185 nm/min) with respect to the operation with a cold target, which is due to the assisting vapour sublimation from custom–designed graphite–based targets. The temperature boosted HT GIMS discharge, proves to be an efficient tool for reaching relatively high (∼35 %) sp3–hybridized C content in both carbon–based materials. It also allows for tailoring the energy bandgap of DLC–based optical structure, in the range from 1.7 to 2.75 eV, due to the formation of the (CC) and (CO) bonds. Higher content of silicon oxide (SiO2-x) and silicon carbide (SiC) phases (15 – 23 %) in the case of C–SiC films results in hardness increase from 21.8 to 30.1 GPa.